TrackRecord: add a method to return callbacks since last poll

This change adds a backtrace() method which returns a list of events
that were received since the last time a user called poll() on a
ReadHead. This is particularly useful for logging observed events while
a poll was in progress that did not end up matching an event.

Test: atest EthernetManagerTest
Change-Id: If019cf9eb5e3e9268c5e6b74edbd8f49959cc71c
1 file changed
tree: 6e50ddadc4cd6f1e3af2f6f99154208542b29446
  1. staticlibs/